1. Field of the Invention
The present invention relates to an apparatus for fracturing polycrystalline silicon which is raw material of semiconductor silicon or the like into fragments, and a method for producing fractured fragments of polycrystalline silicon using the apparatus for fracturing.
Priority is claimed on Japanese Patent Application No. 2010-242059, filed Oct. 28, 2010, the content of which is incorporated herein by reference.
2. Description of Related Art
A silicon wafer which is used for a semiconductor chip is manufactured from single-crystal silicon which is produced by, for example, Czochralski method (“CZ method”). For producing single-crystal silicon by the CZ method, for example, fractured fragments of polycrystalline silicon that is obtained by fracturing rod-shaped polycrystalline silicon formed by Siemens process is used.
For fracturing polycrystalline silicon, as shown in FIG. 9, a rod R of polycrystalline silicon is fractured to fragments C of a few millimeters to a few centimeters. In this process, it is typical to break the rod R into appropriate size by thermal shock or the like, and then further hit and break the fragments with a hammer directly. However, the process strains workers, so that it is inefficient to obtain fragments of appropriate size from rod-shaped polycrystalline silicon.
In Japanese Unexamined Patent Application, First Publication No. 2006-122902, a method for obtain silicon fragments by fracturing rod-shaped polycrystalline silicon with a roll-crasher is disclosed. The roll-crasher is a single-roll crasher in which one roll is stored in a housing and a plurality of teeth are formed on a surface of the roll. The roll-crasher fractures the rod-shaped polycrystalline silicon by collapsing between the teeth and an inner surface of the housing so as to impact the polycrystalline silicon continuously.
However, in this apparatus, powder of polycrystalline silicon is apt to be generated since the fractured fragments of silicon are wedged into a gap between roots of the teeth on the roll and the inner surface of the housing and ground. Therefore, fracturing efficiency of silicon to obtain the fragmented silicon of appropriate sizes is deteriorated. Also, the powder cannot be used for the CZ method since particle size is too small. As a result, this apparatus cannot fracture silicon without loss.
On the other hand, in Published Japanese Translation No. 2009-531172 of the PCT International Publication and Japanese Unexamined Patent Application, First Publication No. 2006-192423, apparatuses for fracturing roughly-crashed fragments of polycrystalline silicon are proposed. These apparatuses are double-roll crashers having two rolls and crashing the roughly-crashed fragments of polycrystalline silicon between the rolls.
In these cases, the apparatuses are not efficient since the fragments of polycrystalline are crashed with being ground between the rolls, so that the powder of polycrystalline silicon is apt to be generated.